Process and apparatus for annealing the weld bead of a welded metallic tube

ABSTRACT

An apparatus for treating continuously welded metallic tubes comprises a series of longitudinal inductors mounted on movable carriages which are adapted to be pivotal co-axially with respect to the tube in response to the angular position of the weld bead formed on the tube so that each of the inductors remains centred on this weld bead.

United States Patent [1 1 Garnier 1 Oct. 23, 1973 PROCESS AND APPARATUSFOR ANNEALING THE WELD HEAD OF A WELDED METALLIC TUBE [75] Inventor:Andre Garnier, Aulnoye-Aymeries,

France [73] Assignee: Vallourec Usines a Tubes de Lorraine-Escaut ctVallourec Reunies, Paris, France [22] Filed: Sept. 14, 1971 [21] Appl.No.: 180,350

[30] Foreign Application Priority Data v Sept. 17, 1970 Luxembourg 61704[52] US. Cl. 219/8.5, 219/1053, 219/1079 [51] Int. Cl. 1105b 5/08 [58]Field of Search 219/85, 10.43, 10.53,

1 1F il l i.

[56] References Cited UNITED STATES PATENTS 3,242,300 3/1966 Osboan219/8.5 3,265,378 8/1966 Grube et al 3,242,299 3/1966 Laughlin et al219/85 Primary Examiner-Bruce A. Reynolds AttorneyBreitenfeld & Levine[57] ABSTRACT 2 Claims, 4 Drawing Figures PROCESS AND APPARATUS FORANNEALING THE WELD BEAD OF A WELDED METALLIC TUBE The present inventionrelates to a process and an apparatus for treating welded metal tubesand more particularly welded tubes made of a steel which has a highelastic limit.

In the production of welded tubes from steel, a continuously travellingstrip is shaped by sets of suitable rollers into a tube, the edges ofwhich are welded in a welding station. The station can operate forexample, by induction with the aid of high frequency currents. It isknown that it is necessary to anneal the weld bead so as to ensure thatthe tube has a uniform elastic limit, this annealing consisting ofmaintaining the weld bead at a well-established and constant temperaturefor a particular period. The heating of the weld bead is effected by aseries of longitudinal inductors which are centred on the welding lineso that the temperature decreases symmetrically on each side of theline. These inductors have to be sufficiently close together and insufficient numbers for the heating line to be homogeneous and remain atthe required temperature for a particular period, allowing for the speedof travel of the tube.

It is known that if the original strip is not perfectly rectilinear, forexample, if it is curved as it has a tendency to be, the weld bead istwisted. That is to say, the bead is not situated in the vertical planecontaining the axis of the tube at a distance from the welding station.Because of this twisting, which may reach several centimetres over alength of a few metres, the weld bead is disposed outside the heatingzone of the last of the series of inductors.

Moreover, the welding generates a temperature gradient which issymmetrical with respect to the weld. This gradient decreases in time,but there is a remanence from the stored heat, which, if twisting occursand if the inductors are fixed, results in the temperature gradientalong a plane perpendicular to the axis of the tube beingnon-symmetrical after passing beneath the inductors. It follows that thetemperature control eyepiece, which if twisting occurs does not sightthe weld bead, indicates an incorrect temperature even if the inductorsheat a zone covering the displacements of the weld bead homogeneously.

In an effort to overcome this disadvantage, it has already been proposedto displace the inductors horizontally, that is to say in a planeparallel to the plane at a tangent to the upper generatrix of the tube,in order to attempt to keep the heat flux centred on the weld bead. Thissimple solution is not sufficient once the weld bead is displacedsubstantially from the upper generatrix of the tube, because the heatingbecomes a symmetrical and the maximum temperature is no longer centredon the weld bead.

The process according to the invention permits the regular heating ofthe weld head, the heating being centred on the weld bead even if arelatively large and variable twisting occurs.

According to the present invention, there is provided a process forannealing the weld bead of a metallic tube which is welded in a weldingstation whilst travelling continuously therethrough, wherein the weldedmetallic tube is caused to pass from the welding station beneath aseries of longitudinal inductors which are centred on the weld bead soas to maintain the bead at an established high temperature for a giventime, each of the inductors being arranged on a movable carriage mountedon a fixed support so as to be pivoted coaxially with respect to thetube, the angular position of each of the carriages being adjusted inrespect to the angular position of the part of the weld bead which isabout to pass beneath the corresponding inductor, whereby the inductoris centred on the weld bead despite twisting of the tube.

According to one embodiment of the invention, the remanence of thetemperature gradient resulting from the heat stored in the metal at thetime of welding is utilised as a control parameter to control theangular position of each carriage. More specifically, the temperatureson opposite sides of the part of the weld bead which is about to passbeneath the inductor carried by the particular carriage are measured bytwo temperature measuring devices rigidly mounted on the carriage. Thecarriage is then positioned so that the measurements effected by thesetwo devices are substantially the same.

Under these conditions, the heating curve of the tube after it emergesfrom the first controlled inductor remains symmetrical and the resultantgradient before passage of the bead beneath the second inductor canserve for centering the latter. Hence, the progress is by degrees andthe different inductors follow the weld bead, even if it follows theform of a flattened sinusoid.

The invention is also concerned with an installation which is suitablefor carrying into effect the process as defined above.

According to the present invention, there is provided an apparatus forannealing the weld head of a continuously travelling welded metallictube, comprising a plurality of longitudinal inductors which arearranged so as to be disposable in series over the centre of the weldbead of a welded tube leaving a welding station, wherein then theinductors are so positioned, the inductors are adapted to be powered byalternating electrical energy so as to keep the temperature of a weldbead at a predetermined high temperature for a'given time, each inductorbeing fixed on a carriage which is pivotal coaxially with respect to thetube and is mounted on guide means rigidly connected to a fixed stand,the angular displacement of each carriage being controllable by a motorwhich is actuatable in the event of there being a difference between theangular positions of the respective inductors and the part of the weldband which is about to pass therebeneath, to reduce the said difference.

Referring to the accompanying drawings:

FIG. 1 is an end view of an embodiment of an apparatus according to thepresent invention,

FIG. 2 is a front view of the embodiment shown in FIG. 1,

FIG. 3 shows the successive arrangement of the inductors which permits agood annealing of the weld to be obtained, and

FIG. 4 shows the temperature distribution obtained after welding andpassage of the weld beneath the different inductors.

FIGS. 1 and 2 show a station for annealing the weld bead of a tube 1,the tube being welded, for example, by induction along the uppergeneratrix in a welding station situated upstream with respect to thedirection of travel of the tube through the annealing station.

The annealing is carried out by means of an inductor 2 which is mountedwith its equipment in a housing 3 for sliding movement on a carriage 7.The displacement of the assembly comprising the inductor 2 and thehousing 3 relative to the carriage 7 can be effected firstly by a screwjack 6 fixed to the carriage and secondly by a hydraulic jack 5 mountedin series with the jack 6 and pivoted at a point 4 on the housing 3.

' The screw jack 6 makes it possible, to regulate the gap between theinductor 2 and the tube 1 as a function of the external diameter of thetube when the rod of the hydraulic jack 5 is fully entered.

The hydraulic jack 5 which is mounted in series with the screw jack 6,is intended to provide for the swift removal of the inductor 2 away fromthe tube 1 inthe event of a production difficulty.

The carriage 7 is provided with rollers, such as 10 and 11, which rollin cylindrical tracks 9. These latter form part of a support 8 whichslides on slideways 12 under the action of a screw jack l3. Adjustmentof the screw jack 13 makes it possible to bring the axes of thecylindrical roller tracks 9 into coincidence with the axis of the tube 1whatever the tube diameter.

A screw jack 14 is mounted on the support 8 and pivoted at a point 15 onthe carriage 7. This jack 14 is actuated by a motor 14a and provides forthe displacement of the rollers 10 and 11 of the carriage 7 in thecylindrical roller tracks 9 of the support 8. Thus, the carriage 7 andall the devices which are fixed thereon, and especially the inductor 2,can be turned about the axis of the cylindrical roller tracks 9 andconsequently about the axis of the tube 1 which coincides with it.

Hence, the assembly 2, 3, 7 is able to turn on either side of the uppergeneratrix of the tube 1, so as to maintain the inductor 2 centred onthe welding line whatever its displacement during manufacture, thespacing from the tube remaining constant.

Preferably the stand 16, on which the support 8, the carriage 7, thehousing 3 and the inductor 2 are mounted can be removed from theproduction line under the action of a hydraulic jack 20. For thispurpose, the stand 16 rests on wheels 17 and 18 which run on rails 19.

Generally, a production line will comprise several successive weld beadannealing stations identical with that shown in FIGS. 1 and 2. Such aline is indicated in FIG. 3, in which the'high frequency inductor of thewelding station is indicated at 21, showing as an example the case inwhich the weld bead twists towards the right.

The successive heating inductors 22, 23 to 27 turn in the samedirection, each of them remaining centred on the weld bead. It isobvious that the number of inductors placed along the weld bead dependson the speed of travel of the tube 1 and the annealing time.

As previously indicated, the angular position of individual inductors isestablished by the jack 14 and is controlled by the angular displacementof the weld bead at the entry to the individual annealing stations. Theactual measuring equipment and also the means permitting the control tobe obtained have not been shown, because they are conventional and wellknown in the art.

Generally, a measuring device which acts on the jack 14 for centeringthe inductor on the weld bead is positioned upstream from each inductor,and a known pyrometric apparatus which measures the maximum temperatureat right angles to the weld head is also provided. The pyrometricapparatus controls the amount of energy which the inductor delivers tothe tube for maintaining the maximum temperature at the correctannealing value.

FIG. 4 shows how the heat is propagated on either side of the weld beadduring the passage thereof beneath the successive inductors, thetemperature maximum remaining constant at a predetermined value andbeing centred on the weld bead. The position of a measuring device inthe form of differential sighting eyepieces LD-l and LD-2 and theposition of a pyrometric control apparatus Lc is indicated.

I claim:

1. Apparatus for annealing the weld bead of a continuously travellingwelded metallic tube, said apparatus comprising a plurality ofcarriages, a plurality of arcuate guides in each of which a carriage ismovable so that the angular position with respect to the axis of thetube being annealed can be adjusted, an inductor extendinglongitudinally of said tube and mounted on each carriage so that itsangular position with respect to said tube is adjustable with movementof said carriages, means for supplying alternating electrical energy tosaid inductor, and a motor to move the carriage with respect to itsrespective guide.

2. Apparatus according to claim 1 including means for adjusting theposition of said guides toward and away from the tube, so that thecenter of curvature of said guides can be made to coincide with thelongitudinal axis of the tube regardless of the diameter of the tube.

1. Apparatus for annealing the weld bead of a continuously travelling welded metallic tube, said apparatus comprising a plurality of carriages, a plurality of arcuate guides in each of which a carriage is movable so that the angular position with respect to the axis of the tube being annealed can be adjusted, an inductor extending longitudinally of Said tube and mounted on each carriage so that its angular position with respect to said tube is adjustable with movement of said carriages, means for supplying alternating electrical energy to said inductor, and a motor to move the carriage with respect to its respective guide.
 2. Apparatus according to claim 1 including means for adjusting the position of said guides toward and away from the tube, so that the center of curvature of said guides can be made to coincide with the longitudinal axis of the tube regardless of the diameter of the tube. 